Created
March 2, 2013 01:53
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Lazy enumerations reduce allocations
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| class LoggedChar < Struct.new(:char) | |
| def downcase | |
| puts "downcasing #{char}" | |
| char.downcase | |
| end | |
| def capitalized? | |
| puts "capitalized? #{char}" | |
| char =~ /[A-Z]/ | |
| end | |
| end | |
| array = %w(a B c D e F g).map { |char| LoggedChar.new(char) } | |
| puts "## NORMAL ITERATION ##" | |
| puts | |
| p array.select(&:capitalized?).map(&:downcase) | |
| puts | |
| puts | |
| puts "## LAZY ITERATION ##" | |
| puts | |
| p array.lazy.select(&:capitalized?).map(&:downcase).to_a | |
| # OUTPUT | |
| # ------ | |
| # | |
| # ## NORMAL ITERATION ## | |
| # | |
| # capitalized? a | |
| # capitalized? B | |
| # capitalized? c | |
| # capitalized? D | |
| # capitalized? e | |
| # capitalized? F | |
| # capitalized? g | |
| # downcasing B | |
| # downcasing D | |
| # downcasing F | |
| # ["b", "d", "f"] | |
| # | |
| # | |
| # ## LAZY ITERATION ## | |
| # | |
| # capitalized? a | |
| # capitalized? B | |
| # downcasing B | |
| # capitalized? c | |
| # capitalized? D | |
| # downcasing D | |
| # capitalized? e | |
| # capitalized? F | |
| # downcasing F | |
| # capitalized? g | |
| # ["b", "d", "f"] |
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